MIAMI (CBSMiami) — Get ready for a rate hike if you plan on becoming a new AT&T customer.

The company raised rates on its Smartphone and tablet data plans.

The new rates will go into effect on Sunday, but only new customers will be affected.

The company’s previous bottom-tier $15 plan will go up to $20, although the amount of data allocated also goes up to 300 from 200 megabytes. Likewise, the $25, 2 gigabyte plan goes up to a $30, 3GB one. Its high-end $45, 4GB plan–which includes the mobile hot-spot capability–goes up to $50 for 5GB.

If you’re already under contract, you’ll keep your current rate.

As mobile data usage increases and carriers run out of spectrum to cram data into, they are raising rates and limiting usage on their networks.

Verizon followed AT&T in July by ending its unlimited offering, and T-Mobile similarly cancelled its unlimited data plan in April.

Sprint remains the lone national carrier that provides unlimited data for its customers.

But all of them have raised prices, ended perks, or stiffened penalties within the last year.

Sprint, for instance, raised its early termination fee in December.

Verizon cancelled its New Every Two bonus discounts a year ago, and T-Mobile began throttling customers speeds when they exceeded their data limits.